If by platforms you mean the streaming services, no, they are not ripping cds or using pcs. I don’t know how the transfer is done but I assume files are sent by the record labels to the streaming services over the internet and stored on servers. Again I don’t know how they send out the streams to individuals, but I’m sure it involves a lot of sophisticated professional computer equipment. These services are not run out of someone’s basement.
Qobuz and Tidal have at least a million albums available, many hi-res. That would be a lot of ripping and hard drives.